# Integer The type to use for an `int` that might be null is `Integer`. ```java ~void main() { Integer i = null; IO.println(i); i = 5; IO.println(i); ~} ``` If you try to do any math on an `Integer` which holds `null` you will get a `NullPointerException`. ```java,panics ~void main() { Integer i = null; IO.println(i * 5); ~} ```